L = list(range(int(input()),int(input())+1))
x = 0
for i in L:
    if i % 2 == 1:
        x += 1
print(x)



# BEGIN
# INPUT(A,B)
# IF(A>5)AND(B<O)
#   THEN
#   X=A+B
# ELSE
#   X=A-B
# END

"""
1 正常值测试
2 边界值测试 
3 异常输入测试


"""

